FINAL PREPARATIONS: 1968

Spacecraft and Mission Progress

Most of MSC's activity during 1967 and early 1968 was directed toward
reducing the fire hazard in the command module. The spacecraft hatch was
redesigned so that the crew could open it unaided in five seconds.
Electrical systems and the plumbing that carried oxygen and combustible
coolants were thoroughly examined and modified. New materials to replace
flammable nylon were investigated. The advantages and disadvantages of
atmospheres other than pure oxygen were weighed. Repeated testing
gathered data to support recommended changes. A Senior Flammability
Board, a Materials Selection Review Board, and a Crew Safety Review
Board were established to oversee specific parts of the process, and a
tough Configuration Control Board was set up to pass on all proposed
changes in the command module. The spacecraft builder, North American
Aviation, was prodded to supervise its subcontractors and vendors more
closely to ensure on-time delivery of critical subsystems.1 The lunar landing module was less affected by
the fire, but it had its own problems. As had happened two years
earlier, its weight continued to creep upward, putting a squeeze on the
scientific payload that could be landed on the moon. Stress corrosion -
cracks in aluminum structural members - and fragile wiring caused delays
and concern for reliability. Perhaps the most serious problem was
combustion instability in the lander's ascent engine, which would blast
the astronauts in the upper section back into lunar orbit after they had
completed their lunar exploration. These were worrisome problems at this
late stage, but concentrated effort by the lunar module contractor and
two engine contractors produced enough progress by mid-1968 to give NASA
managers reason for guarded optimism.2

Late in January 1968 flight tests resumed when MSC put an unmanned lunar
lander through its paces in earth orbit. Designated Apollo 5 and
launched on a Saturn I-B, this flight verified operation of the lunar
module's propulsion and attitude-control systems and checked out the
performance of the instrument unit on the launch vehicle's uppermost
stage, the S-IVB. The success of this mission was more encouraging than
the one that followed. On April 4 Apollo 6, the second
"all-up" unmanned test of the Saturn V, tested launch- vehicle
systems and the emergency detection system and allowed launch crews and
vehicle engineers to rehearse their tasks once more. Along for the ride,
more or less, was a Block I command module with some Block II* modifications; no mission objectives were
to be satisfied by this spacecraft except verification of its
performance during reentry from a lunar mission. Apollo 6 was trouble
from the start. The first-stage burn produced intolerable
"pogo" effects (longitudinal oscillations due to irregular
fuel feed), and a section of the adapter that mated the spacecraft to
the booster blew off during ascent. Two of the five engines on the
second stage (S-II) shut down prematurely. Perhaps the most troublesome
fault was the failure of the third stage (the S-IVB) to reignite in
orbit - the maneuver that, on a lunar mission, would send the Apollo
craft on its way to the moon. Marshall Space Flight Center immediately
got to work on the problems; yet another unmanned Saturn V test might be
needed unless Marshall's engineers could correct them.3

In spite of the difficulties with Saturn V and the lunar module, in
mid-1968 it still seemed possible that manned flights could resume
before the end of the year. Command and service module number 101,
delivered to the Cape at the end of May, had fewer discrepancies on
arrival than any previous spacecraft. It would fly on Apollo 7, the
first manned earth-orbital test of the second-generation spacecraft,
scheduled for the last quarter of the year. Since that mission would use
a Saturn 1-B rather than a Saturn V and would not carry a lunar module,
its prospects seemed good.4

While spacecraft and operations engineers worked toward getting Apollo
flying again, their counterparts in the science programs were equally
busy preparing for the first lunar landing. Of all the science-related
efforts, the lunar surface experiments were in the best shape in early
1968. The lunar receiving laboratory with its complex scientific
equipment, and the elaborate procedures for back-contamination control,
had much farther to go before they would be ready to handle their part
of the program.

* The two versions of the command
module were designed respectively for earth-orbit and lunar-landing
missions. They differed chiefly in onboard systems (guidance and
navigation, docking, life-support, etc.).